Electrodeposition of Porous Fe-Ni-Co Nanowires Using Hydrogen Gas Bubbles

Abstract

The use of hydrogen gas bubbles as a dynamic template accompanied with metal species reduction has recently been used to create porous metal thin films, where the metal deposits within spaces between bubbles. Creating porous nanowires within a nanoporous template is a greater challenge, as the gas bubbles can block the pores of the template, preventing deposition. Thus, the competition between the rate of metal deposition and hydrogen evolution reaction needs to be balanced. While this talk will focus on the electrodeposition process in creating porous metal nanowires, the selected Fe-Ni-Co material serves as a model oxygen electrocatalyst. Conditions making it possible to potentiostatically electrodeposit porous Fe-Ni-Co nanowires using a polycarbonate (PC) nanotemplate are presented. Results show that the pH plays an important role not only in defining the rate of hydrogen evolution, but also the type of metal ion species that are reduced, leading to a change of composition. The porous structure, obtained from the solution having a pH less than 1.0, was confirmed by SEM and TEM. Such an observation is contradictory to the results from anodic alumina oxide (AAO) templates, where no nanowires or very short nanowires were found at the same conditions due to bubble coalescence. The changes in the ionic strength gradient at the electrode surface towards the bulk electrolyte, and the absorbed metal ion intermediates, are suggested to play an important role in deterring bubble coalescence making it possible to create porous nanowires.